In the auto body repair business it is often necessary to clampingly engage and pull upon a section of vehicle body sheet metal in order to assist in straightening the same. Accordingly, many different forms of pull clamps heretofore have been devised for this purpose. However, many of these previously known forms of pull clamps are either time consuming to install and remove, do not afford sufficient clamping action or tend to exert a clamping action which automatically increases an excessive amount as the pull on the clamp to straighten the associated sheet metal panel is increased. Accordingly, a need exists for an improved form of pull clamp which may be readily installed and removed, automatically actuated to apply a sufficient clamping action to prevent slippage and operative to progressively decrease the clamp force-to-pull ratio as the pull on the clamp is increased.
Examples of previously known forms of pull clamps including some of the general structural and operational features of the instant invention are disclosed in U.S. Pat. Nos. 1,457,104, 3,355,777, 3,744,838, 3,827,279, and 3,955,249.